A situation described in the following may help ordinary people understand a background of the present invention. That is, for example, let us consider that a user intends to park his or her vehicle at an intended location in a parking area. The user carefully steers a steering wheel so as not to contact the vehicle with the other vehicles around it or obstacles such as road facilities including a wall and a pillar. The user may need to repeatedly K-turn or pull over to a curb. The user repeatedly drives the vehicle forward and backward and may be at a loss to understand how much the steering wheel is rotated or whether the tires are directed to the right or left. In such a case, the vehicle may move to an unintended direction and collide with an obstacle.
In consideration for such situation, for example, Japanese Patent Document JP-A-1996-80865 (referred to as Patent Document 1 hereinafter) discloses a front tire steering angle indication apparatus that uses a needle to indicate a front tire steering angle corresponding to a steering wheel operation. The apparatus is built in a dashboard at a driver's seat and always indicates the front tire steering angle.
Using that apparatus, the user can relatively easily determine the amount of steering wheel operation to park the vehicle at an intended place.
Even when the user uses the apparatus to successfully park or stop the vehicle, an unexpected accident may occur when the vehicle starts the next time depending on a condition of tires steered to park the vehicle.
As an example, a vehicle 11 may be parked at the end of a road 10 whose cross sectional view is convex as shown in FIG. 1A. FIG. 1B is a top view of the vehicle 11 parked at the end of a lane 12 of the road 10. FIG. 1B assumes that the user parks the vehicle by leaving the steering wheel turned to the left against a traveling direction. When restarting the vehicle, the user may forget correcting the condition of the steering wheel (or a tire 13). The tire 13 may move as steered and sidetrack because it is not positioned straight along the traveling direction. In the worst case, the vehicle may fall from the road.
On the contrary, the user may park the vehicle by leaving the steering wheel turned to the right. When the user inadvertently restarts the vehicle without correcting the condition of the steering wheel, the vehicle may collide with a vehicle coming in the opposite direction on an opposite lane 14 or with another vehicle catching up from behind on the lane 12.
As another example, the user may wait for the traffic light to change and forget turning the steering wheel to the right or left. After the traffic light changes, the user may restart the vehicle without correcting the steering wheel, causing the same accident as mentioned above. The above description obviously applies to driving on not only the left-hand side but also the right-hand side depending on traffic regulations of the subject country.
The apparatus according to Patent Document 1 simply always displays the steering condition of tires despite the above-mentioned situations. The apparatus does not notify whether or not the user needs to pay attention to a steering condition of tires of the stopped vehicle next time the vehicle restarts. Even though the apparatus of Patent Document 1 allows the user to recognize the tire steering condition, the user needs to determine the condition at the time of restarting the vehicle based on his or her experience or intuition. Even when a vehicle uses the apparatus of Patent Document 1, the user may forget confirming the tire steering condition. The user cannot be aware of the condition at the time of restarting the vehicle.
The user may forget a steering condition of tires of the stopped vehicle and restart the vehicle to cause an unsafe condition. The apparatus in Patent Document 1 cannot notify the user that the tires are not steered in a proper direction. In other words, that apparatus cannot provide the necessary notification at a timing needed for the user when the vehicle stops or restarts.